The present invention relates to the field of ophthalmic instruments, and more particularly, to an improved vision tester designed for accurate and precise measurement of visual performance over a variable range of testing distances. The present invention is designed to provide a variety of standard and/or customized vision tests in a relatively small, compact, lightweight, and portable instrument.
Conventional vision testers are described in U.S. Pat. No. 4,740,072. Examples of prior art vision testers are discussed in that patent. That discussion is incorporated by reference herein.
Since the issuance of the ""072 patent, additional vision testers have been suggested including a self testing device described in PCT Application No. PCT/IL97/00220 (International Publication No. WO 98/02083). This application describes a computer-controlled self testing device such as a vision screener. Unfortunately, this computer-controlled device still incorporates many of the drawbacks of conventional testers including testing over a limited number of vision testing distances.
Despite the evolution of vision testing technology generally, there remain drawbacks in existing vision testers. First, there exist apparatuses with tests for near and far vision. Further, as described in the ""072 patent, there may also be intermediate distance tests that may be administered depending on the manual insertion of different lenses and/or prisms in the apparatus. These arbitrary lenses can be inserted in the screener to reproduce different visual distances seen by a test subject. Unfortunately, this testing is very arbitrary, because it can only test certain distances. There is limited variability in the test equipment based solely on the various lenses and prisms that may be inserted into the apparatus.
Second, vision testers that use bulbs or other light sources shining through, for instance, a slide, do not allow for variability in the size of the image presented. In other words, the image itself cannot be enlarged or reduced. The only way to accomplish this variability is to have a plurality of different slides, with each slide having different-sized images. This means an arbitrary library of images that an administrator is limited to.
Also, in some devices, testing vision at different distances requires a different orientation of gaze. Test subjects must be made aware of this fact, and some subjects who do not have experience in the use of multifocal lenses (tilting the head for gazing at different distances) might have problems in realizing this requirement.
Accordingly, it is an object of the present invention to overcome the foregoing drawbacks and provide a vision testing apparatus that solves those problems.
Specifically, the present invention includes a vision test apparatus comprising a light occluding casing. A viewer is connected to the casing and comprises a front lens. A mirror is rotatably mounted to the inside of the casing and behind the front lens. An image display is movably mounted to the inside of the casing. And an auxiliary lens is movably mounted to the inside of the casing and in alignment between the image display and the mirror whereby an image that is displayed on the image display passes through the auxiliary lens, reflects off the mirror and passes through the front lens.
In another embodiment, the invention includes a vision test apparatus comprising a light occluding casing. A viewer is connected to the casing and comprises right and left front lenses. A right mirror and a left mirror are each rotatably mounted to the inside of the casing behind the corresponding right and left front lenses. A right image display and a left image display are movably mounted to the inside of the casing wherein the image displays face each other with each display being generally perpendicular to a line between the corresponding front lenses and mirrors.
In a further embodiment, the vision test apparatus comprises a light occluding casing. Viewing means are fixably attached to the casing. Mirror means are rotatably mounted behind the viewing means for reflecting images from an image display means to the viewing means. There is also included a means for generating images, and an auxiliary lens movably mounted to the casing between the image displays means and the mirror means.